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... Free surface tailoring method is a design method that partial differential equations are solved using numerical values so as to construct the surface figure [1] of free-form surface in lighting optics, it is very widely applied in the field of lighting design. One of the most important steps in designing tailored free-form surface is to calculate [2] the light intensity after light passes through the optical surface with light wavefront as the carrier. As shape of the light wavefront has changed after passing through the optical surface, therefore, changes [3] of the light wavefront curvature tensor and optical surface tensor must also be considered, so that complexity of the differential equation that is required to be ultimately solved is increased. ...
As a new generation of light source, LED has many advantages that other light sources do not have. However, due to the nonuniform lighting of LED, secondary LED optical system design is particularly important. Freeform surface tailoring method, an important method of lighting design, establishes a light intensity change model after smooth surface refraction (reflection) of the light and simplifies the solution process for more complex issues of solution using the free surface tailoring method. Based on this method, secondary LED optical system is designed, and the light intensity distribution is simulated after LED light passes through the secondary optical system. The results show that the method has not only simplified the calculation process of the free surface tailoring method, but also the designed LED secondary optical system has achieved the purpose of uniform lighting to a certain degree.
... We have shown in several previous papers how tailoring can be used for the design of smooth (non-Fresnel) optical surfaces, both in two dimensions, 8,9 and in three dimensions. 10,11 In this contribution we show how the technique can be applied to determine the global shape of Fresnel optical surfaces. ...
The key idea of Fresnel optics is to decouple the global slope from the local slope by breaking up the optical surface into small facets. The size of the facets is irrelevant as long as they are larger than the wavelength of light, so that the system behaves according to geometrical optics, and at the same time small compared the overall size of the optical surface. From the point of view of phase-space conservation, Fresnel optics suffer from a basic shortcoming. The phase-spaces of incoming and outgoing radiation beams need not automatically be equal. This results in either a dilution of radiation or losses or both. On the other hand, decoupling local from global slope allows to tailor the overall shape of the Fresnel lens independently from designing the individual facets. We show that it is possible to closely match incoming and outgoing radiation beams with a particular choice of the global shape of the Fresnel surface. This shape imultaneously minimizes dilution and blocking.
